The United Nations Kyoto Protocol on global warming officially went into effect at 0500 GMT Wednesday, legally binding most of the industrialized countries to control pollution.

The agreement, negotiated in Kyoto, Japan in 1997 by 159 countries and ratified by 141, is an adjunct to the 1992 UN treaty on climate change.

The protocol targets carbon dioxide and five other gases that can trap heat in the atmosphere, and which are blamed for rising global temperatures.

The protocol will have legal force for its participants from February 16 after meeting twin conditions -- backing from at least 55 countries and support from nations representing at least 55 percent of developed countries' carbon dioxide emissions.

It passed the second hurdle in November 2004 when ratified by Russia and now has backing from nations representing 61.6 percent of emissions. The United States, the world's biggest polluter, has pulled out, saying the protocol is too expensive and wrongly omits developing nations.

It commits the industrialized countries that have ratified it to reduce the amount of six greenhouse gases (carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride) by 5.2 percent of 1990 levels during the five-year period from 2008 to 2012.

Only 39 countries have target levels for the period, adhering to the principle set under the United Nations Framework Convention on Climate Change (UNFCCC) that wealthier countries should take the lead.

Under a 2001 deal made by environment ministers in Germany, countries overshooting their targets in 2012 will have to make both the promised cuts and 30 percent more in a second period from 2013.

(Xinhua News Agency February 16, 2005)